The number of echoes combined into a single image or image set in multiple echo imaging sequences or echo-train techniques such as rapid acquisition with relaxation enhancement (RARE), fast-spin echo (FSE), and turbo spin-echo (TSE). In RARE imaging, the ETL typically equals the acceleration factor.
As for tooth pain, it is caused by a reaction of the nerves inside a tooth's pulp chamber with the severity dependent upon the type and degree of the stimulus. What follows are some examples of symptoms you may be feeling and their possible causes.
Throbbing tooth pain is often associated with inflammation in or around the tooth caused by: infection in the center (the pulp) of the tooth; infection of the gums; sinus infection; cracked or chipped teeth; broken crowns or fillings; Whatever sort of pain you experience, sharp or throbbing, your brain is telling you that there is a problem that needs to be fixed. How to Relieve Throbbing Tooth Pain